Method of manufacturing a photovoltaic foil

ABSTRACT

The invention pertains to a method of manufacturing a photovoltaic foil comprising a TCO layer, a photovoltaic layer, and a back electrode, which method comprises the following steps: providing a conductive temporary substrate; applying a TCO layer on the temporary substrate; applying a photovoltaic layer on the TCO by means of electrodeposition, with the current during the electrodeposition being supplied at least through the temporary substrate; applying a back electrode; if so desired, applying a permanent substrate; removing the temporary substrate. The crux of the invention is that the unit of the conductive temporary substrate and the TCO functions as electrode during the electrodeposition of the photovoltaic layer. Because of this, the rate of deposition of the photovoltaic layer can be increased compared with that of the prior art. Furthermore, a photovoltaic layer with a more homogenous layer thickness is obtained.

[0001] The invention pertains to a method of manufacturing aphotovoltaic foil, more particularly a photovoltaic foil where thephotovoltaic layer has been applied by means of electrodeposition.

[0002] Thin film solar cell foils, also known as photovoltaic foils,generally comprise a carrier and a photovoltaic (PV) layer composed of asemiconductor material provided between a front electrode comprising atransparent conductive oxide (TCO) (at the front of the foil) and a backelectrode (at the back of the foil). The front electrode is transparent,enabling incident light to reach the semiconductor material, where theincident radiation is converted into electric energy. In this way lightcan be used to generate electric current, which offers an interestingalternative to, say, fossil fuels or nuclear power.

[0003] In the manufacture of photovoltaic foils generally use is made ofvacuum deposition processes. These processes usually are more expensivethan comparable processes carried out under atmospheric conditions. Forthat reason it is desired to manufacture the active layers undermoderate process conditions at atmospheric pressure. This can beachieved, e.g., by means of electrochemical deposition of thesemiconductor layers. Such processes are known, int. al., from U.S. Pat.No. 4,816,120 and G. C. Morris and R. Vanderveen, Sol. Energy Mater.Sol. Cells 27 (1992) 305. Galvanic (electrochemical) deposition, fromnow on also called electrodeposition, requires that the layer on whichthe deposition takes place is electrically conductive.

[0004] One method for effecting this is using a metallic substrate inthe preparation of the solar cell sheet. Such processes are described inU.S. Pat. No. 4,341,610 and DE 196 34 580. The metallic substratefunctions simultaneously as substrate and as back electrode. Thephotovoltaic foils prepared by this method comprise a metal substrate, aphotovoltaic layer applied by electrodeposition, and a transparentconductive oxide (TCO) as front electrode. However, the order of firstapplying the PV layers and then the transparent conductor layer imposesserious limits on the transparent conductor materials used. E.g., a veryfavourable transparent electrode layer is F-doped tin oxide. However, inorder for this to have the desired properties and texture, it shouldpreferably be applied at a temperature of at least 400° C. Such a hightemperature may be devastating to the PV layers, int. al. as a result ofcrystallisation, diffusion of dopants if present, diffusion ofimpurities, crack formation, and/or loss of hydrogen.

[0005] A further method for using electrodeposition to deposit thephotovoltaic layers is deposition on glass provided with a layer of atransparent conductive oxide (TCO). Raffaelle et al. (R. P. Raffaelle etal., Electrodeposited CdS on CIS pn junctions, Solar Energy Material &Solar Cells 57 (1999) 167-178) describes the subsequentelectrodeposition of CIS and CdS on indium tin oxide coated glass. Daset al. (S. K. Das and G. C. Morris, Preparation and characterisation ofelectrodeposited n-CdS/p-CdTe thin film solar cells, Solar EnergyMaterial & Solar Cells 28 (1993) 305-316) describes the subsequentelectrodeposition of CdS and CdTe on indium tin oxide coated glass. Inthe electrodeposition of cadmium telluride the TCO with the CdS bufferlayer provided thereon is used as electrode. However, a major drawbackto these processes is the low rate of growth of the photovoltaic layers.The rate of growth is limited by the low conduction of the TCO, for therequired electrons have to be transported through this layer. Because ofthe thickness of this layer, typically <1 micron, the resistance ishigh. This in turn means that the rate of growth is dependent on thedistance from the electric contacts provided. Differences in the rate ofgrowth lead to variations in the final layer thickness of thephotovoltaic layer, which is undesirable.

[0006] Attempts have been made to resolve the problem of the lowdeposition rate by providing electric conductors with low resistance,such as metals, on or beneath the TCO in the form of stripes. This makesit possible to employ larger panels while maintaining a more or lessacceptable rate of growth. The drawback to this approach, however, isthat the conductors cast a shade on the active layers, causing adecrease in the current-to-unit area ratio of the modules. Furthermore,in this case the rate of deposition is dependent on the distance fromthe electric conductors, resulting in a photovoltaic layer ofinhomogeneous thickness. According to yet another method, first a thinlayer of conductive metal is applied on the TCO. This will improveconduction to a certain extent, but because the layer of conductivemetal impedes the incident light, it also leads to a reduction of theamount of light in the cell, and hence to a reduction of the amount ofcurrent generated.

[0007] Consequently, there is need for a method of manufacturing aphotovoltaic foil where the photovoltaic layer can be appliedhomogeneously at a high rate of deposition by means ofelectrodeposition, and wherein the nature of the TCO can be selectedindependently from the nature of the photovoltaic layers.

[0008] It was found that this problem can be resolved by applying theTCO on an electrically conductive temporary substrate and supplying thecurrent for the electrodeposition at least through the temporarysubstrate. As a result, the unit of temporary substrate and TCO will actas electrode during the electrodeposition of the PV layer. Obviously,the TCO and the temporary substrate should be in good ohmic contact.Because the substrate is much thicker than the TCO and generally has afar superior conductivity, the amount of current supplied to the systemof substrate and TCO can be increased compared with the prior art. Thisincreases the maximum deposition rate that can be used to obtain ahomogeneous photovoltaic layer. As a result of the high conductivity ofthe substrate, the potential of the TCO is essentially the same acrossthe entire surface. As a result of this, a PV layer of homogeneousthickness is deposited. Because the TCO is deposited on the temporarysubstrate, and not on the photovoltaic layer, the TCO can be selectedindependently from the nature of the photovoltaic layer.

[0009] The invention therefore pertains to a method comprising thefollowing steps:

[0010] providing a conductive temporary substrate

[0011] applying a TCO layer on the temporary substrate under suchconditions that the TCO and the temporary substrate are in good ohmiccontact

[0012] applying a photovoltaic layer by means of electrodeposition onthe TCO layer, with the current for the electrodeposition being suppliedat least through the temporary substrate

[0013] applying a back electrode

[0014] if so desired, applying a permanent substrate

[0015] removing the temporary substrate.

[0016] The conductive temporary substrate preferably is flexible,enabling the process to be carried out in the form of a roll-to-rollprocess. The permanent substrate can be rigid or flexible, depending onthe application. For most applications, the permanent substratepreferably is flexible also. The process according to the invention ispreferably carried out in a continuous process. More preferably, thecontinuous process is a roll-to-roll process.

[0017] An additional advantage of the method according to the inventionis as follows: in order to reduce resistance losses in the photovoltaicfoil, as well as to reduce losses in the frequently required inverter,the photovoltaic foil is often divided up into individual cells, whichare then connected in series. This process entails, int. al., thatgrooves are provided in the TCO layer. In a system where the TCO isapplied on a non-conductive carrier, say, a glass carrier,electrochemical deposition of the photovoltaic layer takes place only onthe TCO, and there is no or hardly any deposition in any grooves thatmay have been provided in the TCO. This makes easy provision of a seriesconnection impossible.

[0018] In the process according to the invention, in which a conductivesubstrate is employed, the photovoltaic layer is also deposited in thegrooves in the TCO, as a result of which a simple series connection canbe made. The method according to the invention is then carried out asfollows: a temporary substrate coated with a TCO with grooves isprovided. By means of electrodeposition a photovoltaic layer is appliedon the TCO and the grooves provided in it. Grooves or (rows of) holesare provided in the photovoltaic layer next to the grooves in the TCO.Then a back electrode is provided with grooves next to the grooves or(rows of) holes provided in the photovoltaic layer. If so desired, apermanent substrate is provided, after which the temporary substrate isremoved. In an alternative way of providing a series connection in theprocess according to the invention, first grooves or (rows of) holes areprovided in the photovoltaic layer. Next, a back electrode is provided,in which grooves are made during the deposition, e.g., by using a mask,or afterwards. The PV-foil together with the back electrode is thenlaminated on a permanent substrate and the temporary substrate isremoved. Then, grooves are provided in the TCO with has becomeaccessible with the removal of the temporary substrate, and optionallyin the PV layer. The grooves can be provided via methods known as such.These include electro-erosive metal removing, wet etching, dry etching,laser ablation, blasting with an erosive powder or frozen liquidparticles, and mechanical scribing with a hard scribing point.

[0019] As indicated above, the crux of the present invention is that theunit composed of the conductive temporary substrate and the TCOfunctions as electrode during the electrodeposition. Because theconductivity of the temporary substrate is higher than that of the TCO,the direction of the current in the TCO will be essentiallyperpendicular to the substrate layer direction. As a result, thepotential of the TCO is essentially homogeneous, resulting in anessentially homogeneous layer thickness of the deposited photovoltaiclayer or layers, with a thickness deviation from the mean of usuallyless than 10%, preferably of less than 5%, more preferably of less than2%.

[0020] An elegant embodiment of the method according to the invention isone in which the temporary substrate with the TCO provided thereon isled over a roller, with the current for the electrodeposition beingsupplied through said roller. This roller rotates in the electrolyterequired for deposition of the PV layer. This results in an extremelyhomogeneous supply of current to the TCO. Furthermore, the system is oftechnological interest, since it is suitable for integration in aroll-to-roll-process.

[0021] In a different embodiment of the method according to theinvention the temporary substrate with provided thereon the TCO isguided via one or more guiding rolls into an electrolyte bath, with theguiding roll or guiding rolls also serving as an electric contact to thefoil. Such a set-up makes it possible for deposition to take place athigh current density, and hence at high speed. When there are highcurrents during deposition and large spaces between the contact rolls,there will be a potential (voltage drop or voltage increase) in themachine direction of the foil which may reduce the rate of growth.Carrying out the process continuously in that case turns out to have anadditional advantage. Since the potential is only present in the processdirection and the foil also moves in this direction, despite thedifference in potential a photovoltaic layer of homogeneous thicknesswill still be formed. A device to practise this process is shown inFIG. 1. In this figure, a temporary substrate provided with a TCO (1) isled via a set of earthed guiding rollers (2) through an electrolyte bath(3) provided with the necessary electrolyte (4). Electrodes (5) providethe necessary current.

[0022] In the process according to the invention, the PV layer isapplied by way of electrodeposition with the current being suppliedthrough the electrically conductive temporary substrate. If so desired,one or more other layers, such as the TCO, the back electrode, and anyoptionally present buffer layers may also be applied by way ofelectrodeposition with the current being supplied through theelectrically conductive temporary substrate. In a particularly favouredembodiment of the process according to the invention the TCO, anyoptionally present buffer layers, the photovoltaic layer, and the backelectrode are each applied by electrodeposition in succession in acontinuous process with the current being supplied through theelectrically conductive temporary substrate.

[0023] In a further variation in a first step, the temporary substrateis prepared by way of electrodeposition on a carrier, e.g., a drum or acontinuous belt, after which the TCO, any optionally present bufferlayers, the photovoltaic layer, and the back electrode are applied byway of electrodeposition to the temporary substrate in succession in acontinuous process. Then, the composition comprising the temporarysubstrate, the TCO, any optionally present buffer layers, the PV layerand the back electrode are removed from the carrier and processedfurther. An apparatus for carrying out this embodiment is presented inFIG. 2. This figure shows an electrodeposition bath (1), divided intovarious segments by way of partitions (2). Each segment contains anelectrode (3) and the electrolyte (4) required for the specificdeposition. An earthed (grounded) drum (5) of, e.g., chromium oxiderotates in the bath. In each section of the bath a layer of thephotovoltaic foil is deposited, starting with the temporary substrate,followed by deposition of the TCO, any buffer layers, the PV layer andthe back electrode. The system (6) comprising temporary substrate, TCO,optional buffer layers, and back electrode is then removed from the bathto be subjected to the further process steps.

[0024] As was indicated earlier, a roll-to-roll process constitutes apreferred embodiment of the method according to the invention. Methodsof manufacturing of thin film solar cell sheets using a temporarysubstrate are known in the art. An especially suitable roll-to-rollprocess is described in WO 98/13882.

[0025] The Temporary Substrate

[0026] The temporary substrate has to satisfy a number of conditions. Ithas to be sufficiently conductive to be able to conduct enough currentduring the electrodeposition of the photovoltaic layer. It has to besufficiently heat-resistant to be able to endure the conditionsprevailing during the manufacture of the thin film solar cell sheet,more particularly during the deposition of the TCO and the PV layer. Ithas to be strong enough to be able to carry the thin film solar cellfoil during its manufacture. It has to be easy to remove from the TCOlayer without damaging the latter. The person skilled in the art will beable to select a suitable temporary substrate within these guidelines.

[0027] The temporary substrate employed in the process according to theinvention preferably is a foil of a metal or a metal alloy. Theprincipal reasons for this are that such foils exhibit goodconductivity, generally are able to withstand high processingtemperatures, are slow to evaporate, and are comparatively easy toremove using known etching techniques. Another reason to choose a metalfoil, more particularly aluminium or copper, is that in the end the thinfilm solar cell sheet has to be provided with edge electrodes which haveto connect the thin film solar cell sheet to an apparatus or theelectricity grid. Pieces of unremoved temporary substrate may be used tothis end, as a result of which there is no need for separate provisionof the edge electrodes. Suitable metals include steel, aluminium,copper, iron, nickel, silver, zinc, molybdenum, chromium, and alloys ormulti-layers thereof. For economic reasons among others it is preferredto employ Fe, Al, Cu, or alloys thereof. Given their performance (andtaking into account the matter of cost) aluminium, iron, optionally madeby electrodeposition, e.g., in the integrated process of FIG. 2, andcopper, optionally made by electrodeposition, e.g., in the integratedprocess of FIG. 2, are preferred most. Suitable etchants and techniquesfor removing metals are known, and while they differ per metal, theskilled person will be able to select the appropriate ones.

[0028] Preferred etchants include acids (both Lewis and Brnstedt acids).Thus in the case of copper it is preferred to use FeCl₃, nitric acid orsulphuric acid. Suitable etchants for aluminium are, e.g., NaOH, KOH,and mixtures of phosphoric acid and nitric acid.

[0029] If copper, optionally prepared by way of electrodeposition, isused as temporary substrate it is preferred to provide the copper,optionally via electrodeposition, with a non-reducing diffusion barrierlayer, e.g., an anti-corrosion layer, more particularly zinc oxide. Thisis because copper may have the tendency to diffuse through the TCO layerin the PV layer. It is also possible to select a TCO capable ofpreventing such diffusion, e.g., SnO₂ or ZnO. The anti-diffusion layerscan be applied by means of for instance electrodeposition, or viaPhysical Vapour Deposition (PVD) or via Chemical Vapour Deposition(CVD). The anti-diffusion layer generally is removed from the TCOtogether with the temporary substrate.

[0030] For ease of removal, the temporary substrate preferably is asthin as possible. Of course, its thickness has to be such that otherlayers can be provided on it and it has to be able to hold thesetogether, but this generally does not require it to be more than 500 μm(0.5 mm) thick. The thickness preferably is in the range of 1 to 200 μm(0.2 mm). Depending on the modulus of elasticity, the minimum thicknessfor a large number of materials will be 5 μm. Accordingly, a thicknessof 5-150 μm, more particularly 10-100 μm, is preferred.

[0031] The TCO Layer

[0032] Examples of suitable transparent conductive oxides (TCOs) areindium tin oxide, zinc oxide, zinc oxide doped with aluminium, fluorine,gallium or boron, cadmium sulphide, cadmium oxide, tin oxide, and, mostpreferably, F-doped SnO₂. Said last-mentioned transparent electrodematerial is preferred, because it can form a desired crystalline surfacewith a columnar light scattering texture when it is applied at atemperature above 400° C., preferably in the range of 500 to 600° C., orafter-treated at said temperature. It is precisely in the case of thisTCO material that the use of a temporary substrate capable ofwithstanding such a high temperature is extremely attractive. Inaddition, the material is resistant to most etchants and has a betterresistance to chemicals than the much-used indium tin oxide. Also, it isfar less costly.

[0033] The TCO can be applied by means of methods known in the field,e.g., by means of Metal Organic Chemical Vapour Deposition (MCCVD),sputtering, Atmospheric Pressure Chemical Vapour Deposition (APCVD),PECVD, spray pyrolysis, evaporation (physical vapour deposition),electrodeposition, optionally in a process integrated in theelectodeposition of the PV layer, electroless plating, screen printing,sol-gel processes, etc. It is preferred to apply and after-treat the TCOlayer at a temperature above 250° C., preferably above 400° C., morepreferably between 500 and 600° C., so that a TCO layer of the desiredcomposition, properties and/or texture can be obtained.

[0034] The Buffer Layer

[0035] If so desired, a buffer layer may be present between the TCOlayer and the photovoltaic layer. The buffer layer is intended toprotect the TCO layer from conditions prevailing during the depositionof the PV layer. The nature of the buffer layer will depend on thenature of the PV layer. Suitable buffer layers for the various PV layersare known in the art. For cadmium telluride CdS, In(OH,S) and Zn(OH,S)may be mentioned. If in the present specification mention is made ofdepositing the PV layer on the TCO, a buffer layer may always be presenton said TCO.

[0036] The Photovoltaic Layer

[0037] After application of the TCO layer the photovoltaic (PV) layer isapplied by means of electrodeposition. It should be noted here that inthe present description the term “PV layer” or “photovoltaic layer”comprises the entire system of layers needed to absorb the light andconvert it into electricity. Suitable layer configurations to be appliedby means of electrodeposition are known, as are the methods for applyingthem. For the common general knowledge in this field reference may behad to Yukinoro Kuwano, “Photovoltaic Cells,” Ullmann's Encyclopedia,Vol.A20 (1992), 161 and “Solar Technology,” Ullmann's Encyclopedia,Vol.A24 (1993), 369. Processes for electrodepositing photovoltaic layersare described in, e.g., U.S. Pat. No. 4,816,120, U.S. Pat. No.5,472,910, U.S. Pat. No. 4,440,244, U.S. Pat. No. 4,456,630, and U.S.Pat No. 4,388,483, as well as in, say, G. C. Morris and R. J.Vanderveen, Applied Surface Science 92 (1996), 630-634. For good order'ssake it is noted that it is not necessary for all sublayers of thephotovoltaic layer to be applied by means of electrodeposition. Cadmiumsulphide for instance can be applied by means of, e.g., CVD, immersion,electroless plating, sputtering or vacuum evaporation, followed by theapplication of cadmium telluride by means of electrodeposition.

[0038] Various thin-film semiconductors can be used in the manufactureof the PV layer by means of electrodeposition. Examples are CIS (copperindium diselenide, CuInSe₂), CuInS₂, cadmium telluride (CdTe), CIGSS(Cu(In,Ga)(Se,S)), Cu(In,Ga)Se₂, ZnSe/CIS, ZnO/CIS, and/orMo/CIS/CdS/ZnO, and dye sensitised solar cells.

[0039] The overall thickness of the PV layer generally will be in therange of 100 to 10000 nm, more particularly between about 200 and 6000nm, preferably between about 250 and 5000 nm, more preferably betweenabout 300 and 1000 nm.

[0040] The Back Electrode

[0041] The back electrode in the thin film solar cell sheet according tothe invention preferably serves both as reflector and as electrode.Generally, the back electrode will have a thickness of about 50 to 500nm, and it may comprise any suitable material having light reflectingproperties, preferably aluminium, silver, or a combination of layers ofboth, and making good ohmic contact with the subjacent semiconductorlayer. Preferably, it is possible to apply the metal layers at acomparatively low temperature, say less than 250° C. , by means of,e.g., electrodeposition, (in vacuo) physical vapour deposition orsputtering. In the case of silver, it is preferred to first apply anadhesion promoter layer. TiO₂, TiN, ZnO, and chromium oxide are examplesof suitable materials for an adhesion promoter layer and have theadvantage of also possessing reflecting properties when applied in asuitable thickness, e.g., of 50-100 nm. The required back electrode maybe either transparent or opaque The back electrode preferably is appliedby electrodeposition, optionally in a process integrated in theelectodeposition of the PV layer.

[0042] The Permanent Substrate

[0043] Although it is not essential to the process according to theinvention, as a rule it is preferred to provide the thin film solar cellsheet with a permanent substrate. For, otherwise the thin film will beso thin that its fragility makes for difficult handling. When employed,the permanent substrate is applied on the back electrode. Suitablesubstrate layer materials include thin films of commercially availablepolymers, such as polyethylene terephthalate, poly(ethylene2,6-naphthalene dicarboxylate), polycarbonate, polyvinyl chloride, PVDF,PVDC, or thin films of polymer having very good properties such asaramid or polyimide thin films, but also, for example, metal foils ontowhich an insulating (dielectric) surface layer may have been applied, orcompositions of plastics and reinforcing fibres and fillers. Polymeric“co-extruded” thin films provided with a thermoplastic adhesive layerhaving a softening point below that of the substrate itself arepreferred. If so desired, the co-extruded thin film may be provided withan anti-diffusion layer of, e.g., polyester (PET), copolyester oraluminium. The thickness of the substrate preferably is 50 μm to 10 mm.Preferred ranges are 75 μm to 3 mm and 100 μm to 300 μm. The bendingstiffness of the substrate, defined within the context of thisdescription as the product of the modulus of elasticity E in N/mm² andthe thickness t to the power of three in mm (E×t³), preferably is higherthan 16×10⁻² Nmm and will generally be lower than 15×10⁶ Nmm.

[0044] The substrate may comprise a structure as required for its finaluse. Thus the substrate may comprise tiles, roofing sheets and elements,facade elements, car and caravan roofs, etc. In general, however,preference is given to the substrate being flexible. In that case a rollof thin film solar cell sheet is obtained which is ready for use andwhere sheets of the desired power and voltage can be cut off the roll.These can then be incorporated into (hybrid) roof elements or be appliedonto tiles, roofing sheets, car and caravan roofs, etc., as desired.

[0045] If so desired, a top coat or surface layer may be provided on theTCO side of the solar cell to protect the TCO from outside influences.Generally, the surface layer will be a polymer sheet (with cavities ifso desired) or a polymer film. The surface layer is required to have ahigh transmission and for instance comprises the following materials:amorphous (per)fluorinated polymers, polycarbonate,poly(methylmethacrylate), PET, PEN or any clear coating available, suchas the ones used in the car industry. If so desired, an additionalanti-reflection or anti-fouling layer may be provided. Alternatively, ifso desired, the entire solar cell may be incorporated into such anencapsulant.

1. Method of manufacturing a photovoltaic foil comprising a TCO layer, aphotovoltaic layer, and a back electrode, which method comprises thefollowing steps: providing a conductive temporary substrate applying aTCO layer on the temporary substrate applying a photovoltaic layer onthe TCO by means of electrodeposition, with the current for theelectrodeposition being supplied at least through the temporarysubstrate applying a back electrode if so desired, applying a permanentsubstrate removing the temporary substrate.
 2. The method according toclaim 1 in which the temporary substrate with the TCO provided thereonis led over a roller, with the current for the electrodeposition beingsupplied through said roller.
 3. The method according to claim 1 inwhich the temporary substrate provided with the TCO is guided via atleast one guiding role into an electrolyte bath containing an electrode,with the guiding role or roles also serving as electric contact for thefoil.
 4. The method according to any one of the preceding claims whereinone or more layers selected from the TCO layer, any electricallyconductive buffer layers and the back electrode are also applied by wayof electrodeposition with the current being supplied through thetemporary substrate.
 5. The method according to claim 4, wherein the TCOlayer, any electrically conductive buffer layer, the photovoltaic layerand the back electrode are applied by way of electrodeposition insuccession in a continuous process.
 6. The method according to claim 5,wherein in a first step the temporary substrate is prepared byelectrodeposition on a carrier, after which the TCO layer, anyelectrically conductive buffer layer, the photovoltaic layer and theback electrode are applied by way of electrodeposition in succession ina continuous process.
 7. The method according to any one of the claims1-5 wherein the temporary substrate is a metal foil.
 8. The methodaccording to any one of the preceding claims wherein a buffer layer isprovided between the TCO and the photovoltaic layer.
 9. The methodaccording to any one of the preceding claims comprising the followingsteps: providing a temporary substrate applying a TCO with groovesprovided therein applying a photovoltaic layer on the TCO and thegrooves provided therein by means of electrodeposition providing groovesor (rows of) holes in the photovoltaic layer next to the grooves in theTCO applying a back electrode provided with grooves next to the grooves(or rows of) holes in the photovoltaic layer if so desired, applying apermanent substrate removing the temporary substrate.
 10. The methodaccording to any one of claims 1-8 comprising the following steps:providing a temporary substrate applying a TCO applying a photovoltaiclayer by means of electrodeposition providing grooves or (rows of) holesin the photovoltaic layer applying a back electrode provided withgrooves if so desired, applying a permanent substrate removing thetemporary substrate providing grooves in the TCO.
 11. The methodaccording to any one of the preceding claims which is carried out in acontinuous process, preferably in a roll-to-roll process.